Here, in the second episode of the series, Sir David Attenborough looks at the curious cases of the duck-billed platypus and the male Midwife Toad.
When early explorers brought back the first duck-billed platypus specimen to England in 1799 it was deemed so bizarre by scientists that it was thought to be a hoax, baffling even the great Charles Darwin.
The duck-billed platypus mystified scientists due to both its intriguing mammal and bird-like characteristics - a coating of fur alongside a bill and webbed feet. They also lay eggs like a bird but produce milk like a mammal.
Where does this animal sit in the tree of life?
But how did this tiny toad baffle the scientific community?
This species of toad is unique because they breed on land while the male is the one who carries the string of fertilised eggs on his back, hence the name "midwife".